\ print the current stack using .s

\ for example:
1 2 .s
\ --> <2> 1 2  ok

\ it lists the number of items on the stack in angle
\ brackets, followed by the content of the stack, and then
\ ok

\ print the top element of the stack
1 2 3 .
\ --> 3 ok
1 2 3 . . .
\ --> 1 2 3 . . . 3 2 1  ok
